E. de Kaenel, G. Vi lla : Helicosphaera carteri: furth er note ........ , p. 105- 106.

Journal of Nannoplankton Research, 20, 2, 1998.

HELICOSPHAERA CARTER!: A FURTHER NOTE ON ITSSTRATIGRAPHICAL OCCURRENCE
Eric de Kaenel* & Giuliana Villa***DPR, Motile 51 , CJ-1-2000 Ne uchatel, Switzerland Dipt. di Scienze del/a Terra, **Universita di Pamta, f;iale delle
Scienze 78, 43100 Parma, Italy
This note constitutes a reply to the recent publication inthe J NR of a paper on Helicosphaera carteri by Kic;:oVathi (Vathi , 1998). In this paper, the author extended therange of H. carteri down into the Early Oligocene. In orderto clarify this occurrence, we (de Kaenel and Villa) arereferring to our 1996 publication.
We would like to clarify the presence in Oligocene
sediments of nannofossils almost sim.ilar to H. carteri. Thismay help to avoid future mistakes in nannofossil
biostratigraphy. We have illustrated in our paper anhelicolitl1 identical to the fonns illustrated by vntlu. Contrary
to Vathi , we did not consider these helicoliths as being H.
carteri. Because we noted some different morphologicalfeatures (i.e. the outline of the flange, the features of theproximal plate), and because its range is discontinuous
witl1 reference to tJ1e uppennost Oligocene-LowerMiocene
forms, we decided to use a different taxonomic label:
Helicosphaera alf. H. carteri. In the future, it may be betterto raise this form to the rank of another species or of an
intraspecific t~t-.;on .
Systematic descriptions
Helicosphaera carteri (Wallich, 1877) Kamptne1; 1954
Description: Small- to mediwn-sized Helico,,phaera withan asymmetrical outline. The proximal plate has two verysmall central openings aligned with the principal suture ofthe helicolith. The blanket covered most of the distal
surface. The flange is continuously rounded, witlwut abrupt
diminution of the length of the distal elements, and thetermination of the flange is along the upper part of the sideof the helicolith. The elements of the wing (widest part ofthe flange) may vary greatly in size.
Hoiotype: Coccosphere from the Recent, Indian Ocean(Wallich, 1877, Pl.l7, fig.4).
Size: Coccosphere of Wallich ( 1877): about 1/830 of aninch(= 301J.m). Recent specimens (H. carteri var. carteri):4-12)1111. Miocene specimens: 6- I 5 ).U11 (size depends mostly
on the development of the flange) .
Occurrence: Upper NP25-Recent. Correlation with theeustatic sea-level chart of Haq et al. (I 987): the firstoccurrence (FO) of H. carteri coincides with the base of
the transgressive period oftl1e TB l.3 sequence (de Kaenel& Villa, I 996). Aubry & Villa (1997) reported the FO of H.
carteri in the Lemme-Carrosio section (GSSP for thePalaeogene!Neogene System Boundary), some 29m above
the Oligocene/Miocene boundary, in Nannofossil Zone
NN2 (latest Chron C6Bn.ln at 22.6Ma). This position iscorrelated with the end of the transgressive period TB 1.4.
De Kaenel & VLila (1996) reported tl1e FO of H. carteri
at Hole 900A, some 35m below the NP25/NN l boundary,and in Zone NP25 (earliest Chron C7n.2n at 25.10 Ma). This

event is·recorded a few metres below the level of the lastconsistent occurrence (LCO) of Sphenolithus ciperoensis,
the age of which is estimated at 24.69Ma. The LCO S.
ciperoensis event of de Kaenel & Villa ( 1996) is equivalent
to the last occurrence (LO) of S. ciperoensis of Aubry &Villa (1997). which is dated at 24.7Ma.
Helicosphaera paleocarteri (Theodoridis, 1984)
has its FO in middle NN I at Hole 900A. This form differsfrom 1!. carteri by its proximal plate: tl1e two small open.ings
are not aligned with the principal suture of the helicolith.
Helico!>phaera aff. H. carteri (Wallich, 1877)
Kamptner, 1954de Kaenel & Villa , I 996, p. I25 , p1.8, figs 21-24; pi.IO, figs
14, 15Size: 8-1 O).Un.
Occurrence: Base NP2 3-NP24 (Leg 149, Hole 900A); baseNP23-upperNP23 (Leg 149, Hole897C); lowermost NP25
(Leg 149, Hole 899B, single occurrence, possibly reworked).
Remarks: (from de Kaenel & Villa, p.l25) , This mediumsi zed Helicosphaera has two distinct openings alignedwith the longer axis of the shield. The flange is rounded
and tenninates by a small inner crescent -shaped expansion
along the side oftl1e slueld. The bar is in optical continuity
with the rim and separates two openings. This helicolithmeasures between 8 to l 0 11111 and has a short range
restricted to Oligocene Zone NP23 to tJ1e early part of Zone
NP24. In cross-polarized light, Helico.sphaera aif. H. carteri
exhibits the same intense birefringence as H. carteri and isdistinguished from the latter by its smaller size, the larger
openings and the abrupt termination of the flange ."As also observed by Vathi in land section fromAlbania, we did not observe He/icosphaera all H. carteri
in the lower and middle interval of Zone NP25 and weconcluded that H. carteri is quite unlikely to represe nt are-entry of the same species.
The FO of Helicosphaera aff. H. carteri is used asa secondary Oligocene event in de Kaenel & Villa ( 1996,p .9 1). Its FO is observed between the LO ofReticulofenestra umbilicus and the LO of Lanternithus
minutus.

RcfHcnccs
Aubry. M .-P. & Villa , G. 1997 . Calcareo us n a nn ofossil
strati g rap hy or th e Lemme-Carrosio Pa lcogc ne/Neoge ne
Stratotype Section and point (N W It a ly). G iorn a la diGeologia, ser. 3a, S8(1-2) 1996:5 1-69.
Haq, B .U., Hardenbol , J. & Vail, P.R . 1987. Chronology ofFluctuating Sea Level s Since the Triass ic. Science , 235:1156-11 67.

105

Journal of Nannoplankton Research, 20, 2, 1998.

E. de Kaenel. G. Villa: Helicosphaera carter!: further note ...... , p. 105- 106.

Kaenel, E. de & Villa, G. 1996. Oligocene-Miocene CalcareousNannotossil Biostratigraphy and Paleoecology from the Iberia
Abyssal Plain. Proc. ODP, Scientific Results, 149: 79-145.
Kamptner, E. 1954. Untersuchungen iiber den Feinbau derCoccolithen. Archiv fiir Protistenkunde, 100: 1-90.
Steininger, F.F., laccarino, S & Cati, F. (Eds). 1997. In search of
the Paleogene/Neogene Boundary. Part 3. The global
stratotype section and point (GSSP) for the base of theNeogene (The Paleogene/Neogene Boundary). Gioma la diGeologia, ser. 3a , 58(1-2) 1996.

Theodoridis, S.A. 1984. Calcareous nannofossil biozonation of
the Mioccne and revision of the helicoliths and discoasters.
Utrecht Micropaleontological Bulletins, 32: 1-271.
Vathi, K. 1998. A note on the first occurrence of Helicosphaera
carteri in the Early Oligocene (NP23, Sphenolithus
predistentus Zone). Jo urnal of Nannoplank/on Research ,20(1): 39-43.
Wallich , G.C . 1877. Observations on the coccospherc. Annals
and Magazine of Natural History, 19:342-350.

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